The present invention concerns a method for the reinforcement of concrete, especially the reinforcement of a concrete beam, where the reinforcement comprises reinforcement rods which extend longitudinally and transversely in several layers, where the layers of reinforcement rods are controlled at mutual distance by means of cutouts in the side of lists which are positioned transversely to the layers of reinforcement rods, and the reinforcement rods and the lists are connected at their mutual intersection points with a first spring shackle of a known type.
The invention also concerns a reinforcement for use in the execution of the method.
Concrete which is strengthened by the moulding-in of steel rods is known as reinforced concrete. Due to the reinforcement, reinforced-concrete constructions are not only able to withstand pressure but also traction, bending and twisting.
The reinforcement rods can be in the form of rib bars which have corrugations or ribs on the surface in order to be able to transfer the forces between reinforcement and concrete. In a horizontal reinforced-concrete beam which is simply supported at both ends and influenced by a downwardly-directed load, there is therefore provided a strong reinforcement, the main reinforcement, in the underside of the beam, which is exposed to tractive forces, while a weaker reinforcement, the assembly reinforcement, is provided in the upper side of the beam.
Both the main reinforcement and the assembly reinforcement consist of reinforcement rods which, depending on the dimensions of the beam, extend in a parallel manner at a mutual distance, and both reinforcements are further connected with loops of thinner reinforcement rods, so that the overall reinforcement constitutes a cage in which the positioning of the rods at their mutual intersections is ensured by binding with steel wire. Such a reinforcement cage is lowered into the shuttering, or the shuttering is built up around the reinforcement cage, after which the reinforcement is cast in concrete.
The binding with wire is carried out because it is extremely important that the reinforcement rods lie placed with very small tolerances inside the finished beam. Two reinforcement rods, which cross each other, shall thus be placed within a distance of 5 mm, but since the ribs on the reinforcement rods are 2 mm, two reinforcement rods which rest on the ribs are already 4 mm from each other, so the tolerance for the positioning is hereby down to 1 mm.
With the known reinforcement technique, this requires that the mutual positioning of the reinforcement rods must be carefully controlled prior to each individual binding, which also in itself requires considerable effort. Consequently, the mounting of the reinforcement rods is time-consuming and herewith costly.
A reinforcing of concrete substantially of the above-mentioned kind is known from U.S. Pat. No. 1,835,806. The publication deals with a reinforcement in a road plate of concrete, where the lists with their one end abut against the underlayer, and where there are shown two parallel, horizontal layers of reinforcement rods which cross one another in each layer.
In the one side of the lists there are cutouts, in that in the formation of the uppermost cutout there is made a simple vertical cut, after which the web formed hereby is bent at right-angles in relation to the plane of the lists as support for a reinforcement rod, which extends at right-angles to the plane of the lists. For further support of the reinforcement rod, the outer side of the web is bent slightly upwards in the formation of a bed for the reinforcement rod. A lower-lying cutout is provided in a corresponding manner.
A layer of reinforcement rods, which extends transversely to the plane of the lists, is placed in the cutouts, after which the layer of reinforcement rods extending longitudinally is positioned underneath the first layer abutting against the underside of the above-mentioned webs and secured by means of spring shackles.
Each of the spring shackles has a short and a long leg, each leg extending up from an arc which lies up against the underside of a longitudinal reinforcement rod around a transverse reinforcement rod in a cutout. The short leg is disposed on that side of the list where the cutout's web protrudes, and the short leg ends here. The long leg extends further on the opposite side of the list, i.e. on that side facing away from the web, and is fixed by being crossed under the longitudinally-extending reinforcement rod where it is held in a fixed manner by means of a hook on the end, said hook lying up against the longitudinally-extending reinforcement rod.
The known spring shackle thus has two different legs; a short leg and a long leg.
From U.S. Pat. No. 4,073,112 there is known a reinforcing system for use in a reinforced concrete construction. The means in this reinforcement consist of reinforcement rods and lists which have cutouts for the engagement of the reinforcement rods along an outer side. The function of the lists is to form a frame, where a reinforcement rod can be placed in a corner in a cutout in the formation of the overall reinforcement.
None of these publications disclose a technique which is suitable for reinforcing a reinforced-concrete beam, where a particularly accurate positioning of the reinforcement rods must take place both in relation to each other and to the surface of the finished concrete beam. Moreover, the known spring shackles are not of a configuration which makes them usable in such reinforcement.